Interbody spacer

ABSTRACT

An interbody spacer is provided including a body portion, first orifices, and second orifices. The body portion includes a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies. The body portion includes a cavity defined through the first side surface and the cavity increases in volume at an interior portion of the body portion. The first orifices are defined through the top surface and the second orifices are defined through the bottom surface. One of the first orifices has a cross-sectional configuration different from that of one of the second orifices. A method of use therefor is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and the benefit of, U.S.Provisional Patent Application Ser. No. 62/108,197, filed on Jan. 27,2015 and U.S. Provisional Patent Application Ser. No. 62/196,371, filedon Jul. 24, 2015. The entire contents of each of these priorapplications are hereby incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to an apparatus for treating spinalconditions, and more particularly, to an interbody spacer and a methodof use therefor.

2. Background of Related Art

The human spinal column is a highly complex structure. It includestwenty-four discrete bones, known as vertebrae, coupled sequentially toone another to house and protect critical elements of the nervoussystem. The vertebrae interlock with one another to form a spinalcolumn. Each vertebra has a cylindrical bony body (vertebral body), twopedicles extending from the vertebral body, a lamina extending from thepedicles, two wing-like projections extending from the pedicles, aspinous process extending from the lamina, a pars interarticularis, twosuperior facets extending from the pedicles, and two inferior facetsextending from the lamina.

The vertebrae are separated and cushioned by thin pads of tough,resilient fiber known as inter-vertebral discs. Inter-vertebral discsprovide flexibility to the spine and act as shock absorbers duringactivity. A small opening (foramen) located between each vertebra allowspassage of nerves. When the vertebrae are properly aligned, the nervespass through without a problem. However, when the vertebrae aremisaligned or a constriction is formed in the spinal canal, the nervesget compressed and may cause back pain, leg pain, or other neurologicaldisorders.

For many reasons, such as aging and trauma, the intervertebral discs canbegin to deteriorate and weaken, potentially resulting in chronic pain,degenerative disc disease, or even tearing of the disc. Ultimately, thedisc may deteriorate or weaken to the point of tearing and herniation,in which the inner portions of the disc protrude through the tear. Aherniated disc may press against, or pinch, the spinal nerves, therebycausing radiating pain, numbness, tingling, and/or diminished strengthor range of motion.

Many treatments are available to remedy these conditions, includingsurgical procedures in which one or more damaged intervertebral discsare removed and replaced with a prosthetic. After a partial or completediscectomy, the normally occupied space between adjacent vertebralbodies is subject to collapse and/or misalignment due to the absence ofall or part of the intervertebral disc. In such situations, thephysician may insert one or more prosthetic spacers between the affectedvertebrae to maintain normal disc spacing and/or the normal amount oflordosis in the affected region.

Typically, a prosthetic implant is inserted between the adjacentvertebrae and may include pathways that permit bone growth between theadjacent vertebrae until they are fused together. However, there existsa possibility that conventional prosthetic implants may be dislodged andmoved from their desired implantation location due to movement by thepatient before sufficient bone growth has occurred.

Bone growth is a key factor in ensuring adequate retention of theimplant to the vertebra. Specifically, bone ingrowth within and aroundthe prosthetic implant promotes fusion between the adjacent vertebra,thereby strengthening the joint therebetween. However, conventionalimplants do not allow optimal space for bone ingrowth. In theseinstances, as the prosthetic implants do not mimic bone density of theadjacent vertebra, the body rejects the implant, and non-union (i.e., nofusion) occurs.

Conventional prosthetic implants are typically constructed in a mannerthat inhibits bone ingrowth, particularly those that include no spacesor avenues for such bone growth to occur within and around theprosthetic implant. The lack of fusion may allow the implant to becomedislodged or moved from its desired location. Additionally, in theinstances where the prosthetic implant includes a lumen for the packingof ingrowth material, the material is often able to dislodge from thelumen, and in some instances, from the implant, thereby reducing thechances that adequate bone ingrowth occurs.

Therefore, a need exists for a prosthetic implant that can mimic thedensity of bone or adequately retain ingrowth material therein to allowfor optimal bone ingrowth and provide a solid fusion of the vertebralsegments.

SUMMARY

In accordance with an embodiment of the present disclosure, there isprovided an interbody spacer including a body portion having a distalend portion, a proximal end portion, first and second side surfaces thatextend between the distal and proximal end portions, and top and bottomsurfaces configured and adapted to engage vertebral bodies. The bodyportion includes a cavity defined through the first side surface and thecavity increases in volume at an interior portion of the body portion.First orifices are defined through the top surface and second orificesare defined through the bottom surface. One of the first orifices has across-sectional configuration different form that of one of the secondorifices.

In embodiments, the cavity may include undercuts defined therein. Aninterior dimension of the cavity may increase in a direction towardseach respective top and bottom surface. The cavity may include a greekcross cross-sectional configuration.

In embodiments, each of the first and second side surfaces may includean arcuate configuration. The body portion may define a kidney shapedconfiguration.

In embodiments, one of the first orifices may be offset from one of thesecond orifices. One of the first orifices may include a circularcross-section. One of the second orifices may include a diamond-shapedcross-section. One of the first orifices may include a circularcross-section and one of the second orifices may include adiamond-shaped cross-section.

In embodiments, the interbody spacer may be formed using an additivemanufacturing process.

In embodiments, a portal may be defined through the second side surface.A threaded aperture may be defined through the proximal end portion. Thethreaded aperture is configured to threadably engage an insertion tool.

In embodiments, a plurality of ridges may be disposed on each of the topand bottom surfaces. Longitudinal grooves may be defined through eachplurality of ridges.

In accordance with another embodiment, a method of performing spinalsurgery is provided. The method includes preparing an intervertebralspace between first and second vertebral bodies and advancing aninterbody spacer into the intervertebral space. The interbody spacerincludes a body portion having a distal end portion, a proximal endportion, first and second side surfaces that extend between the distaland proximal end portions, and top and bottom surfaces configured andadapted to engage vertebral bodies. The body portion includes a cavitydefined through the first side surface and the cavity increases involume at an interior portion of the body portion. First orifices aredefined through the top surface and second orifices are defined throughthe bottom surface. One of the first orifices has a cross-sectionalconfiguration different form that of one of the second orifices.

In embodiments, advancing the interbody spacer may include the interbodyspacer having a cavity that includes undercuts defined therein.

In embodiments, the method may include packing the cavity with bonein-growth material. The method may include packing the cavity withdrugs.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described hereinbelowwith reference to the drawings, wherein:

FIG. 1 is rear, perspective view, of an interbody spacer provided inaccordance with the present disclosure;

FIG. 2 is a top, plan view, of the interbody spacer of FIG. 1;

FIG. 3 is a side, elevation view, of the interbody spacer of FIG. 1;

FIG. 4 is a rear view of the interbody spacer of FIG. 1;

FIG. 5 is a cross-sectional view of the interbody spacer of FIG. 1,taken along section line 5-5 of FIG. 3; and

FIG. 6 is a cross-sectional view of the interbody spacer of FIG. 1,illustrating an orifice defined through a top surface being offset froman orifice defined through a bottom surface.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure are now described in detail withreference to the drawings in which like reference numerals designateidentical or corresponding elements in each of the several views. Ascommonly known, the term “clinician” refers to a doctor, a nurse, or anyother care provider and may include support personnel. Additionally, theterm “proximal” refers to the portion of the device or component thereofthat is closer to the clinician and the term “distal” refers to theportion of the device or component thereof that is farther from theclinician. In addition, for the purposes of this application, the term“lateral” indicates a direction toward a side of the body of thepatient, i.e., away from the middle of the body of the patient. The term“posterior” indicates a direction toward the patient's back, and theterm “anterior” indicates a direction toward the patient's front.Additionally, in the drawings and in the description that follows, termssuch as front, rear, upper, lower, top, bottom, and similar directionalterms are used simply for convenience of description and are notintended to limit the disclosure. In the following description,well-known functions or constructions are not described in detail toavoid obscuring the present disclosure in unnecessary detail.

Referring now to the drawings, FIGS. 1-5 illustrate one embodiment of aninterbody spacer provided in accordance with the present disclosuregenerally identified by reference numeral 100. Interbody spacer 100includes a body portion 102 illustrated as having a generally arcuate,kidney shape (FIG. 2); however, it is contemplated that body portion 102may include any suitable shape such as square, rectangular, circular,oval, or the like. As best illustrated in FIG. 2, body portion 102includes an arcuate, first end surface 104, at a distal or leading end106, and a second end surface 108, having a corresponding arcuateprofile to first end surface 104, opposite thereto at a proximal ortrailing end 110. It is contemplated that first and second end surfaces104, 108 may include other, non-corresponding combinations of profiles,such as arcuate and planar, planar and arcuate, and the like. Bodyportion 102 extends between first and second end surfaces 104, 108 todefine respective top and bottom surfaces 112 and 114 (FIG. 3),respectively, as well as side surfaces 116, 118 (FIG. 2). As bestillustrated in FIG. 4, top surface 112 approximates bottom surface 114in a direction from side surface 118 towards side surface 116, althoughit is contemplated that top and bottom surfaces 112, 114 may besubstantially planar relative to one another, approximate in a directionfrom side surface 116 towards side surface 118, approximate in aproximal direction, approximate in a distal direction, or anycombination thereof. Additionally, top and bottom surfaces areillustrated as being substantially planar, although other configurationsare also contemplated such as convex, concave, or the like. A distalportion of top and bottom surfaces 112, 114, respectively, approximatealong a distal direction (FIG. 3) in order to facilitate insertionwithin the intervertebral space and enhance the atraumatic character ofbody portion 102. In this manner, the intersection of top and bottomsurfaces 112, 114 with each of the first and second end surfaces 104,108 and side surfaces 116, 118 may include a fillet or roundedconfiguration 120 to inhibit sharp edges from causing trauma to thesurrounding tissue and/or vertebral bodies. Side surfaces 116, 118 areillustrated as being curved, forming rounded sides, however, it iscontemplated that side surfaces 116, 118 may be planar. Although sidesurfaces 116, 118 are illustrated as curving in the same direction(i.e., side surface 116 is concave and side surface 118 is convex), itis contemplated that side surface 116 may curve in an opposite directionto that of side surface 118 (i.e., side surfaces 116, 118 are bothconvex), or side surfaces 116, 118 may curve toward each other (i.e.,side surfaces 116, 118 are both concave).

Body portion 102 includes a through-bore or cavity 124 defined throughside surface 116 although it is contemplated that through-bore 124 maybe defined through side surface 118. As best illustrated in FIGS. 1 and5, through-bore 124 defines a generally oval configuration through sidesurface 116 and increases in volume at an interior portion of bodyportion 102. The increase in volume permits through-bore 124 to receivea greater amount of biological material than is possible with athrough-bore having planar side walls. In embodiments, the through-bore124 may include any suitable cross-section when viewed along a planeextending vertically and/or horizontally through top and bottom surfaces112, 114 and side surfaces 116, 118, such as spheroid, ovoid, ellipsoid,cuboid, pyramidal, cylindrical, trapezoidal, greek cross, clover,amorphous, or the like. In one non-limiting embodiment, through-bore 124includes upper and lower undercuts 124 a and 124 b adjacent sidesurfaces 116, 118, respectively (FIG. 5), defining a generally greekcross profile. Although the wall thickness of each of top and bottomsurfaces 112, 114 and side surface 118 are illustrated as having asubstantially similar thickness, it is contemplated that top and bottomsurfaces 112, 114 may include one wall thickness and side surface 118may include a thinner or thicker wall thickness, or any combinationthereof.

It is contemplated that through-bore 124 may receive allograft material,autograft material, calcium phosphate/bone marrow aspirate (BMA),autogenous material, synthetic materials comprised of a biocompatible,osteoconductive, osteoinductive, or osteogeneic material such as VITOSS®Synthetic Cancellous Bone Void Filler material, or any other suitablebiological material known in the art. The increase in interior volume ofthrough-bore 124 aids in retaining the biological material therein,reducing the possibility that the biological material may becomedetached from interbody spacer 100. Through-bore 124 includes across-sectional area or surface area that is greater than any orifice ofthe plurality of orifices detailed hereinbelow. In embodiments,through-bore 124 includes a surface area that is equal to or greaterthan 25% of the surface area of side surface 116.

With reference to FIG. 4, a portal 126 is defined through a proximalportion of opposed side wall 118 and extending into through-bore 124. Inthis manner, portal 126 and through-bore 124 are in open communication.Portal 126 allows bone ingrowth and in embodiments, is an attachmentpoint for a suitable insertion instrument (not shown).

With reference to FIGS. 1 and 4, second end surface 108 includes athreaded aperture 122 defined therethrough and extending intothrough-bore 124, thereby placing threaded aperture and through-bore 124in open communication. Threaded aperture 122 is configured to releasablyengage a suitable insertion tool (not shown), such as that described inU.S. Patent Application Serial No. 2012/0158062, filed Oct. 11, 2011,the entire contents of which are hereby incorporated by referenceherein.

Top and bottom surfaces 112, 114 of body portion 102 are configured toengage respective endplates of adjacent vertebral bodies. In thismanner, a plurality of ridges or projections (i.e., teeth) 128 (FIG. 3)is disposed on each of top and surfaces 112, 114 to aid in securinginterbody spacer 100 to each respective adjacent vertebral body andstability against fore and aft, oblique or side to side movement ofinterbody spacer 100 within the intervertebral space. Specifically,ridges 128 frictionally engage endplates of adjacent vertebral bodiesand inhibit movement of the spinal implant 100 with respect to theadjacent vertebral bodies. In embodiments, a longitudinal groove 130(FIG. 2) may be defined through the plurality of ridges 128 on a distalportion of top and bottom surfaces 112, 114.

Interbody spacer 100 is constructed of a biocompatible material, such ascommercially pure titanium and includes a porosity capable of promotingbone ingrowth and fusion with a vertebral body. In this manner, top andbottom surfaces 112, 114 and opposed side surfaces 116, 118 have asurface roughness that can promote bone growth and fusion with interbodyspacer 100. The surface roughness may be in a range of about 0.10-50 μm,and preferably in a range of about 3-4 μm. As can be appreciated, topand bottom surfaces 112, 114 and opposed side surfaces 116, 118 mayinclude the same or different surface roughness's (i.e., the surfaceroughness of top surface 112 may be different than the surface roughnessof bottom surface 114), or top and bottom surfaces 112, 114 and opposedside surfaces 116, 118 may not include a surface roughness; rather, topand bottom surfaces 112, 114 and opposed side surfaces 116, 118 may besmooth. In embodiments top and bottom surfaces 112, 114 and opposed sidesurfaces 116, 118 may include any combination of surface roughness orsmooth surface. Additionally, a plurality of orifices 132 is definedtherethrough configured to promote bone ingrowth. The plurality oforifices 132 is defined through each of top and bottom surfaces 112, 114and side surfaces 116, 118 and may include any suitable cross-sectionsuch as circular, oval, square, hexagonal, rectangular, diamond, or thelike. As can be appreciated, the plurality of orifices 132 definedthrough each of top and bottom surfaces 112, 114 and side surfaces 116,118 may include the same cross-section or different cross-section, orcombinations thereof (i.e., an intermixing of circular and diamondcross-sections on the same surface or different surfaces). In onenon-limiting embodiment, the plurality of orifices 132 defined throughtop and bottom surfaces 112, 114 include a circular cross-section,whereas the plurality of orifices 132 defined through each of sidesurfaces 116, 118 include a generally diamond shaped cross-section.

The plurality of orifices 132 mimic bone growth along Haversian canalsand lamellar structures of bone. In this manner, the plurality oforifices passes entirely through top and bottom surfaces 112, 114 andside surfaces 116, 118. Alternatively, the plurality of orifices 132 maybe offset in relation to one another (FIG. 6). In this manner, anorifice 132 defined through bottom surface 114 will be offset from acorresponding orifice 132 defined through top surface 112. Inembodiments, orifices 132 may be defined through top and bottom surfaces112, 114 and side surfaces 116, 118 normal thereto or at angles relativethereto. In one non-limiting embodiment, orifices 132 are definedthrough top and bottom surfaces 112, 114 at angles incident relative toeach other, thereby forming a chevron configuration. As can beappreciated, each of the orifices 132 formed through top and bottomsurfaces 112, 114 and opposed side surfaces 116, 118, respectively, forma respective channel therebetween, thereby interconnecting an orificeformed through top surface 112 and an orifice formed through bottomsurface 114, or an orifice formed through side surface 116 and anorifice formed through side surface 118. It is contemplated that thedensity of orifices 132 may be different on each of top and bottomsurfaces 112, 114 and side surfaces 116, 118, respectively, or mayincrease or decrease in density at various location thereon. Theplurality of orifices 132 includes diameters in a range of about 50-1000μm, although diameters between 300-700 μm are preferable. As can beappreciated, for shapes other than circular, orifices 132 include across-sectional area in a range of about 0.0019 μm²-0.785 μm², althougha cross-sectional area between 0.0707 μm²-0.385 μm² is preferable. Ascan be appreciated, the plurality of orifices 132 may include orifices132 having varying sizes and shapes relative to each other. Theplurality of orifices 132 reduce the density and stiffness of interbodyspacer 100 to enable the application of bone putty or the like (e.g.,bone morphogenetic proteins, etc.) to interbody spacer 100 to promotebone ingrowth and fusion of adjacent vertebral bodies secured tointerbody spacer 100. Bone ingrowth and fusion strengthen interbodyspacer 100, thereby reducing the probability that interbody spacer 100would fracture and the likelihood that micromotion would occur wouldlikewise be reduced. Alternatively, it is contemplated that interbodyspacer 100 be constructed without orifices 132 defined therethrough,such that exterior surfaces of interbody spacer 100 have a smooth,uniform texture.

As can be appreciated, manufacturing interbody spacer 100 using standardmachining methods (e.g., lathe, mill, EDM, etc.) could be difficult. Inview of this, it is contemplated that in addition to manufacturinginterbody spacer 100 using the aforementioned conventional means,interbody spacer 100 may be manufactured by means of additivemanufacturing methods (e.g., SDM, SLPP, DMLS (i.e., EOS), SLS, SLM, SHS,EBM, VAT photopolymerisation, material jetting, binder jetting, or thelike). In one non-limiting embodiment, interbody spacer 100 is may bemanufactured using Selective Laser Powder Processing (SLPP). SLPPutilizes powdered metal and a laser which sinters or cures the metal ina selective fashion according to the design intent in thin layers. Inembodiments, the layers have a thickness of about 250 μm. Interbodyspacer 100 is built layer by layer to allow for more design options andfeatures that would be difficult to be machined using conventionalmethods. Specifically, a first layer of powder is applied to aspecialized build plate, at which point the laser cures portions of thepowder according to the design intent. At this point, a second layer isapplied to the build plate and the laser is again used to cure selectiveportions of this second layer. This process is repeated until interbodyspacer 100 is fully formed. Once interbody spacer 100 is fully formed,uncured powder is removed using compressed air or other similar means.Next, post machining is performed on interbody spacer 100 to remove anyburrs or similar imperfections embedded within interbody spacer 100during the additive manufacturing process. In embodiments, the burrs areremoved by means of buffer wheels, clippers, files, or the like. Oncede-burred, interbody spacer 100 is heat treated, and thereafter, mediablasted using aluminum oxide. Thereafter, interbody spacer 100 isimmersed in a hydrofluoric bath to strip the aluminum oxide therefrom.Finally, interbody spacer 100 is inspected by quality control personnel(or using automated means), cleaned via ultrasonic cleaning, dried, andpackaged. It is contemplated that the design of interbody spacer 100 maybe customized for each specific patient using SLPP. For a detaileddescription of exemplary manufacturing methods, reference may be made toU.S. Pat. No. 8,590,157, issued on Nov. 26, 2013 to Kruth et al., theentire contents of which are hereby incorporated by reference herein.

Interbody spacer 100 may be constructed from commercially pure titanium,titanium alloy, cobalt-chrome, ceramic, Polyetheretherketone (PEEK), orany other suitable biocompatible material. In embodiments, interbodyspacer 100 may be manufactured using a three-dimensional printerutilizing a biocompatible polymer.

With reference to FIGS. 1-5, in use, an intervertebral space is firstprepared, e.g., damaged or diseased tissue is removed. Thereafter, anappropriately sized interbody spacer 100 is selected based on thepatient's spinal characteristics and the desired amount of lordosis.Next, the interior space of through-bore 124 of body portion 102 may bepacked with bone in-growth material, drugs, or other suitable biologicalmaterials or compounds. Examples of such materials are allograftmaterial, or synthetic materials comprised of a biocompatible,osteoconductive, osteoinductive, or osteogeneic material such as VITOSS®Synthetic Cancellous Bone Void Filler material. Next, a suitableinsertion instrument (not shown) is threaded into threaded aperture 122of body portion 102 until interbody spacer 100 is securely affixed tothe insertion instrument. At this point, interbody spacer 100 isadvanced within an incision within the patient, and thereafter, into thepreviously prepared intervertebral space of the patient's spine. Onceinterbody spacer 100 is placed within the intervertebral space such thatinterbody spacer 100 rests on the distal apophyseal ring of thevertebral body, the tool (not shown) is released from threaded aperture122, and thereafter, removed from the incision within the patient.Residing on the apophyseal ring facilitates fusion between theintervertebral plates and interbody spacer 100, as interbody spacer 100is less likely to experience subsidence into the end plates.

This process may be repeated as many times as the procedure requires,whether it be for the same interbody spacer 100 or for a plurality ofinterbody spacers 100 as required by the procedure being performed.

It is envisioned that the manufacturing processes and orifice designsdetailed above may be utilized to form various other medical devicesknown in the art. In this manner, the additive manufacturing processdetailed above may be employed to form corpectomy devices, fixed spinalimplants, expandable spinal implants, bone screws, cervical implants,and the like. Similarly, the orifice designs detailed above may beformed in any of the beforementioned medical devices that would benefitfrom an increased ability to fuse with bone. Examples of such devicesmay be found in the following commonly owned references: U.S. Pat. No.8,585,761 to Theofilos, U.S. Pat. No. 8,673,011 to Theofilos et al.,U.S. application Ser. No. 14/936,911 to Sutterlin et al., U.S. Pat. No.8,801,791 to Soo et al., U.S. Pat. No. 8,439,977 to Kostuik et al., U.S.Patent Application Publication No. 2010/0100131 to Wallenstein, U.S.Patent Application Publication No. 2012/0179261 to Soo, U.S. Pat. No.8,449,585 to Wallenstein et al., U.S. Pat. No. 8,814,919 to Barrus etal., U.S. Pat. No. 5,733,286 to Errico et al., and U.S. PatentApplication Publication No. 2013/0046345 to Jones et al.

It will be understood that various modifications may be made to theembodiments of the presently disclosed interbody spacer. Therefore, theabove description should not be construed as limiting, but merely asexemplifications of embodiments. Those skilled in the art will envisionother modifications within the scope and spirit of the presentdisclosure.

What is claimed is:
 1. An interbody spacer comprising: a body portion including a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies, wherein the body portion includes a cavity defined through the first side surface, the cavity increasing in volume at an interior portion of the body portion; first orifices defined through the top surface; and second orifices defined through the bottom surface, one of the first orifices having a cross-sectional configuration different from that of one of the second orifices.
 2. The interbody spacer of claim 1, wherein the cavity includes undercuts defined therein.
 3. The interbody spacer of claim 1, wherein an interior dimension of the cavity increases in a direction towards each respective top and bottom surface.
 4. The interbody spacer of claim 1, wherein the cavity includes a greek cross cross-sectional configuration.
 5. The interbody spacer of claim 1, wherein each of the first and second side surfaces includes an arcuate configuration.
 6. The interbody spacer of claim 1, wherein the body portion defines a kidney shaped configuration.
 7. The interbody spacer of claim 1, wherein one of the first orifices is offset from one of the second orifices.
 8. The interbody spacer of claim 1, wherein one of the first orifices includes a circular cross-section.
 9. The interbody spacer of claim 1, wherein one of the second orifices includes a diamond-shaped cross-section.
 10. The interbody spacer of claim 1, wherein one of the first orifices includes a circular cross-section and one of the second orifices includes a diamond-shaped cross-section.
 11. The interbody spacer of claim 1, wherein the interbody spacer is formed using an additive manufacturing process.
 12. The interbody spacer of claim 1, wherein a portal is defined through the second side surface.
 14. The interbody spacer of claim 1, wherein a threaded aperture is defined through the proximal end portion, the threaded aperture configured to threadably engage an insertion tool.
 15. The interbody spacer of claim 1, wherein a plurality of ridges is disposed on each of the top and bottom surfaces.
 16. The interbody spacer of claim 15, wherein a longitudinal groove is defined through each plurality of ridges.
 17. A method of performing spinal surgery, comprising: preparing an intervertebral space between first and second vertebral bodies; and advancing an interbody spacer into the intervertebral space, the interbody spacer including: a body portion including a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies, wherein the body portion includes a cavity defined through the first side surface, the cavity increasing in volume at an interior portion of the body portion; first orifices defined through the top surface; and second orifices defined through the bottom surface, one of the first orifices having a cross-sectional configuration different from that of one of the second orifices.
 18. The method according to claim 17, wherein advancing the interbody spacer includes the interbody spacer having a cavity that includes undercuts defined therein.
 19. The method according to claim 17, further including packing the cavity with bone in-growth material.
 20. The method according to claim 17, further including packing the cavity with drugs. 